Mariposa County Potential Heat Risk for Wednesday ranges from Moderate in the lower elevations to Low in the higher elevations.
September 25, 2019 - The National Weather Service Hanford Office reports high temperatures Wednesday afternoon will be near the daily records for maximum temperatures ever observed in Fresno and Bakersfield on September 25th.
Temperature records at Fresno date back to 1888. Temperature records at Bakersfield date back to 1893.
Area Forecast Discussion National Weather Service Hanford CA 404 AM PDT Wed Sep 25 2019 .SYNOPSIS... Dry weather and well above normal temperatures will continue through Thursday. A significant day to day cooling trend will occur Friday through next Monday and may be accompanied by showers over the Sierra and adjacent foothills this weekend. && .DISCUSSION... We are a couple of days into Autumn but currently experiencing a period of hot and dry summer like conditions. Temperatures will trend further upward today and highs are expected to top out around 8-12 degrees above climo, more typical of late July/early August rather than late September. This warmup is being aided by an offshore flow regime between high pressure building in from the north and an upper level low spinning near northern Baja. After near record highs today, a change in the synoptic pattern will start us on a path to more fall like conditions. Models prog the northern Baja low to lift out after today while a developing low pressure system drops south through the Pacific Northwest by the end of the week. Conditions Thursday will be less hot, but still warmer than seasonal averages in weakening offshore flow during the transition of the pattern. Significant cooling will then commence for the end of the week into the start of next week as the developing low pressure trough continues to drop southward. Temps Friday will at or slightly below climo and by Sunday we`ll see highs as much as 10 to 15 degrees below normal. This system has some moisture with it, and will bring a chance for showers over the Sierra and adjacent foothill zones Saturday through Monday. A bit of accumulating snow will be possible over the high Sierra during the period. Total amounts should be no more than a couple of inches at the highest elevations. Though other areas in central CA are expected to remain mainly dry, blended model guidance does allow for a possibility of light showers along the east side of the SJ Valley up against the foothills with the passing system this weekend. Increasing gusty winds will be the more significant impact outside the Sierra zones over the weekend, especially through the mountain passes and into the desert areas of Kern County on Saturday. As the trough pulls away after Monday, temperatures will recover a bit into the middle of next week but still remaining several degrees below climo.
Source: NWS
